Various types of drinking straws are known for flavouring or changing the flavour of a liquid passing through the drinking straw. Such drinking straws can impart different flavours (e.g. cocoa, fruit, etc.) to a liquid for example milk.
There are solutions in which the flavouring agent is applied on a portion of the drinking straw and dissolves when this portion is immersed in the liquid. Patent application U.S. Pat. No. 3,615,595 describes such flavouring drinking straw. In another embodiment according to U.S. Pat. No. 3,615,595 the flavouring agent is applied on the inner wall of the drinking straw. A disadvantage of this solution is that dissolution of the flavouring agent thereby the flavouring effect is unsatisfactory.
Another common way of disposing the flavouring or other active agents within the drinking straw is by providing granules that contain the flavouring or other active agents that are progressively imparted to a liquid drawn through the drinking straw. A problem associated with this type of flavouring is that the granules have to be retained within the straw. Various devices have been suggested in the prior art for overcoming this problem.
Patent applications U.S. Pat. No. 6,482,451 B1 and U.S. Pat. No. 8,334,003 propose the use of filters the apertures of which are smaller than the cross-section of the granules whereby the liquid can be drawn through the apertures but the granules are retained. The proposed filters are in the form of end caps, whereby the manufacturing costs are increased: the filters need to be manufactured as separate elements and need to be affixed to the drinking straw in a separate manufacturing step. In practice the affixing is carried out by welding the wall of the straw and the inserted end cap from the outside whereby an external seam is formed on the outside of the wall of the straw. The sharp edges around the external seam have to be removed, which requires a further manufacturing step and may still leave unsmooth surface regions.
The problem of having to provide a separate filtering cap is partly overcome in the prior art. Patent application US 2008/0197141 A1 discloses a filled drinking straw both end parts of which are pressed together in a direction perpendicular to the longitudinal axis of the drinking straw thereby creating a narrow passage in order to prevent the undissolved flavouring granules from exiting the straw. By pressing the end parts the plastic body of the tube may also be pressed in a certain extent. To avoid this braces are placed in the tube near the pressed portion. However, if the tube is pressed transversally, large sized fillings can not be fixed in given portions of the tube since they may crack. Furthermore, flow of liquid is restricted because the cross-section is narrowed down to a single harrow passage, which is easily blocked by fillings. Another disadvantage is that sharp edges are formed on the outer surface of the pressed portion which might be inconvenient for the user and in particular for young children who will generally attempt to take more than the mouth piece into their mouth.
Patent application US 2008/0075809 proposes a drinking straw wherein the dissolvable granules are retained by crimping the straw body near the two ends which creates closures that slightly open when liquid is being drawn through the straw thereby allowing the liquid and the dissolved substances to pass through a narrow passage. This solution has for disadvantage that the opening of the crimps cannot be controlled whereby a smaller or larger passage might be created depending on the sucking force applied by the user. A further disadvantage associated with this type of retaining means is that the active ingredient concentration of the liquid drawn through the single narrow passage might vary substantially in time, since it is determined by the local concentration at the opening of the passage. Also such a single passage may be easily blocked by a filler such as a granule.
A further disadvantage of both of the above mentioned solutions is that the wall of the drinking straw is heated from the outside when deforming the straw. During this operation the straw can only be exposed to a heat that does not cause melting, since that would destroy the straw. Furthermore, the straw is generally made of a shape-memory plastic, generally polypropylene, therefore the crimped or otherwise deformed straw may reopen later on.
US 2012/0228400 A1 discloses integral filters formed from the sidewall of the drinking straw adjacent the ends thereof. According to a preferred embodiment the integral filter is formed by clamping and bonding the opposing sides of the tube ends such that an external seam is created, and by perforating the bonded side walls in order to allow liquid communication therethrough but retain the flavouring granules. The disadvantage of such an integral filter is that in spite of trimming any sharp corners along the seam uneven edges may remain that could be inconvenient for a user or even hurt or cut the mouth of the user, especially young children. The edges of the apertures may also be sharp or have inconvenient irregularities presenting the same disadvantage. According to other embodiments the integral filter is formed by cutting and folding or by deforming the tube end such as to cover most of the straw opening and by leaving only a narrow central aperture. The cut or deformed tube ends as well as the edges of the central aperture have the same disadvantage as explained before, furthermore, the deformed portions may reopen during use.
It is an object of the present invention to overcome the problems associated with the prior art. In particular, it is an object of the invention to provide a drinking straw filled with fillers such as flavouring granules that does not contain filters or other inserts and wherein retention of the fillers is achieved by deforming a portion of the drinking straw. A further object is to provide a permanent and durable deformation of the straw in order to retain the fillers. It is a further object to create a user friendly deformed portion that cannot cut or otherwise hurt the mouth of the user. It is a further object not to hinder the liquid flow through the straw. A further object is to simplify manufacturing of the straw and to reduce the costs thereof by eliminating the need of filters, since such filters are manufactured as separate pieces that need to be fixed inside the straw in a separate manufacturing step.
The inventors have recognised that the above objects can be achieved if the straw is deformed spaced apart from its ends such that the inside of the straw is heated at given points (locations) for a short period in order to melt the inner surface of the wall and then the melted points are pressed together. In this case an internal seam is formed at the melted and pressed points. Complete closure of the cross-section of the straw is preferably ensured by applying spacers that create parallel passages between the pressed portions whereby the deformed portion of the straw is in the form of a branched portion. The plurality of passages ensure adequate liquid flow through the deformed branched portion and are less easily blocked than a single passage. This method also allows for fixing various filling elements along the straw, which can be fixed in the same manner. It should be appreciated that when fixing such a filling element the straw is pressed to such an extent only so as to securely hold the filling element the desired location.